A Levels of ULK1 in MEFs exposed to hypoxia (1% O2) for the indicated times.
actin, Western blot

B Quantification of the ratio of ULK1 to actin in (A).

C Levels of ULK1 in MEFs treated with FCCP (20 μM) for the indicated times.

actin

D Quantification of the ratio of ULK1 to actin in (C).E MEFs were exposed to hypoxia (1% O2) for 12 h or FCCP (20 μM) for 6 h and then fixed by 4% paraformaldehyde. Cells were stained with anti‐TIM23 (mouse) and anti‐ULK1 (rabbit) primary antibodies, then Alexa Fluor‐488‐labeled donkey anti‐rabbit IgG and Alexa Fluor‐555‐labeled donkey anti‐mouse IgG secondary antibodies before analysis by immunofluorescence microscopy. Scale bar, 10 μm.

F Immunoblots of subcellular fractions from control MEFs or MEFs that were exposed to hypoxia (1% O2) for 12 h. PNS, post‐nuclear supernatant; Cyto, cytosol; Mito, mitochondria.

ULK1

G Immunoblots of subcellular fractions from control MEFs or MEFs that were treated with FCCP (20 μM) for 6 h. PNS, post‐nuclear supernatant; Cyto, cytosol; Mito, mitochondria.

ULK1

A HeLa cells were co−transfected with FUNDC1−Myc and FLAG−ULK1. Cells were lysed and immunoprecipitated with anti−Myc antibody 24 h after transfection.B FLAG−FUNDC1 was co−transfected with GFP−vector or GFP−ULK1 for 24 h in HeLa cells, and then, cell lysates were immunoprecipitated with anti−GFP antibody.

CMEFs were exposed to hypoxia (1% O2) for 12 h or FCCP (20 μM) for 3 h, followed by immunoprecipitation using anti‐ULK1 antibody.

D The expression of FUNDC1 is induced by 10 ng/ml tetracycline (Tet) in FUNDC1‐inducible HeLa cells. Cells were transfected with HA‐ULK1 or HA‐ULK1 (K46N) for 24 h. Then, the cell lysates were prepared for immunoblotting using indicated antibodies.

EULK1+/+ cells were transfected with FUNDC1‐Myc, and ULK1-/- cells were transfected with FUNDC1‐Myc alone, FUNDC1‐Myc and HA‐ULK1, or FUNDC1‐Myc and HA‐ULK1 (K46N). Cells were harvested and lysed for immunoblots24 h after transfection.

F Purified GST‐FUNDC1 and GST‐FUNDC1 (S17A) were subjected to an in vitro kinase assay with Myc‐ULK1 immunoprecipitated by anti‐Myc antibody from Myc‐ULK1‐transfected cells about 24 h post‐transfection. Phosphorylated FUNDC1 was detected by anti‐p‐S17‐FUNDC1 antibody. The red asterisks mark the target bands.

G Western blotULK1, FUNDC1, and the phosphorylated FUNDC1 in MEFs exposed to hypoxia (1% O2) for the indicated times.

HWestern blot analysis of the kinetics of ULK1, FUNDC1, and the phosphorylated in MEFs treated with FCCP(20 μM) for the indicated times.

actin

I, J The single mutant which can abolish the ULK1 and FUNDC1 interaction was identified. HeLa cells were co‐transfected with Flag‐ULK1 and the indicated constructs. 24 h after transfection, cells were lysed for immunoprecipitation by anti‐Flag antibody.

KMEFs were transfected with FUNDC1‐Myc and its mutants after the endogenous FUNDC1 was knocked down by siRNA. 36 h after transfection, cells were harvested in the absence or presence of 50 nM bafilomycin A1 (BAF1) and then lysed for immunoblotting with the indicated antibodies.

L MEFs were co‐transfected with FUNDC1‐Myc or its mutants and MitoDsred after the endogenous FUNDC1 was knocked down by siRNA. 24 h post‐transfection, cells were treated with hypoxic (1% O2) conditions for 12 h or FCCP (20 μM) for 6 h before fixed by 4% paraformaldehyde and stained with indicated antibodies. Scale bar, 10 μm.

AULK1+/+ and ULK1−/− cells were cultured under hypoxic (1% O2) condition for 12 h or 24 h in the absence or presence of 50 nM bafilomycin A1 (BAF1). Cell lysates were immunoblotted.

B ULK1+/+ and ULK1−/− cells were treated with FCCP (20 μM) for the indicated times in the absence or presence of 50 nM bafilomycin A1 (BAF1). Cell lysates were immunoblotted.C ULK1+/+ and ULK1−/− cells were transfected with FUNDC1−Myc for 24 h and then harvested in the absence or presence of 50 nM bafilomycin A1 (BAF1). Cell lysates were immunoblotted.

D ULK1−/− cells were transfected with HA‐ULK1 or HA‐ULK1 (K46N), then cultured under hypoxic (1% O2) conditions for 24 h in the absence or presence of 50 nM bafilomycin A1 (BAF1). Cells lysates were immunoblotted.

EULK1−/− cells were transfected with HA−ULK1 or HA−ULK1 and then treated with FCCP (20 μM) for 24 h. Cells were harvested in the absence or presence of 50 nM bafilomycin A1 (BAF1). Cell lysates were immunoblotted.

F FUNDC1‐knockdown MEFs were transfected with FUNDC1‐Myc or FUNDC1-Myc (S17A) for the indicated times. Cell lysates were used for immunoblotting.

G ULK1+/+ cells were transfected with FUNDC1‐Myc, and ULK1−/− cells were transfected with FUNDC1‐Myc or FUNDC1-Myc (S17D). 24 h after transfection, cells were fixed with 4% paraformaldehyde and stained with anti‐Myc (mouse) and anti‐LC3 (rabbit) primary antibodies for immunofluorescence microscopy. Scale bar, 10 μm.

H ULK1−/− cells were transfected with FUNDC1‐Myc or FUNDC1-Myc (S17D) for 24 h in the absence or presence of 50 nm bafilomycin A1 (BAF1) for an additional 6 h before harvesting. Cell lysates were immunoblotted.

I ULK1−/− cells were transfected with FUNDC1‐Myc or FUNDC1-Myc (S17D) for 24 h in the absence or presence of 50 nm bafilomycin A1 (BAF1) for an additional 6 h before harvesting. Cell lysates were detected with the citrate synthase activity kit.

J HeLa cells were transfected with FUNDC1‐Myc, FUNDC1-Myc (S17A), or FUNDC1-Myc (S17D). 24 h after transfection, cell lysates were immunoprecipitated with anti‐LC3 antibody.

A ULK1+/+ or ULK1−/− cells were cultured under hypoxic (1% O2) or normoxic conditions in the absence or presence of 50 nM bafilomycin A1 (BAF1). ULK1−/− cells were transfected with HA‐ULK1, and ULK1−/− FUNDC1‐KD cells were transfected with HA‐ULK1 and FUNDC1‐Myc, then cultured under hypoxic (1% O2) conditions for 24 h in the absence or presence of 50 nM bafilomycin A1 (BAF1). Cells were harvested and lysed for immunoblotting assays.B ULK1+/+ or ULK1−/− cells were treated with or without FCCP (20 μM) in the absence or presence of 50 nM bafilomycin A1 (BAF1). ULK1−/− cells were transfected with HA‐ULK1 and ULK1−/− FUNDC1‐KD cells were transfected with HA‐ULK1 and FUNDC1‐Myc and then treated with FCCP (20 μM) for 24 h in the absence or presence of 50 nM bafilomycin A1 (BAF1). Cells were harvested and lysed for immunoblotting assays.C ULK1+/+, ULK1−/− FUNDC1‐KD, or ULK1−/− FUNDC1‐KD cells rescued by introduction of HA‐ULK1 and FUNDC1‐Myc were cultured under hypoxic (1% O2) conditions for 24 h or with FCCP (20 μM) for 24 h. Samples were analyzed by electron microscopy. Scale bar, 2 μm. The yellow asterisks mark mitochondria. The red arrows indicate double‐membraned autophagic structures. The yellow arrow denotes autolysosomes.D-E The mitochondrial coverage and mitochondrial−containing AVs shown in (C) were quantified. Recon, reconstitution.